The applicability of Local Stability Theory (LST), Parabolized Stability Equations (PSE) and the Adaptive Harmonic Linearized Navier-Stokes (AHLNS) approach is investigated in the presence of 2-D surface irregularities through comparison with Direct Numerical Simulations (DNS). Remarkably good agreement between DNS and AHLNS is obtained for the amplification curves of Tollmien-Schlichting (TS) waves in all the cases studied. The LST and PSE results exhibit differences which are discussed in relation to the local distortion of the boundary layer induced by the irregularities.